Abstract

Background

Heavy metal pollution in crop fields is one of the major issues in sustainable agriculture
production. To improve crop growth and reduce the toxic effects of metals is an ideal
strategy. Understanding the resilience of gibberellins producing endophytic fungi
associated with crop plants in metal contaminated agriculture fields could be an important
step towards reducing agrochemical pollutions. In present study, it was aimed to screen
and identify metal resistant endophyte and elucidate its role in rescuing crop plant
growth and metabolism during metal stress.

Results

Fungal endophyte, Penicillium funiculosum LHL06, was identified to possess higher growth rate in copper (Cu) and cadmium contaminated
mediums as compared to other endophytes (Metarhizium anisopliae, Promicromonospora sp. and Exophiala sp.). P. funiculosum had high biosorption potential toward copper as compared to cadmium. An endophyte-metal-plant
interaction was assessed by inoculating the host Glycine max L. plants with P. funiculosum during Cu (100 μM) stress. The Cu application adversely affected the biomass, chlorophyll
and total protein content of non-inoculated control plants. The control plants unable
to synthesis high carbon, hydrogen and nitrogen because the roots had lower access
to phosphorous, potassium, sulphur and calcium during Cu treatment. Conversely, P. funiculosum-association significantly increased the plant biomass, root physiology and nutrients
uptake to support higher carbon, hydrogen and nitrogen assimilation in shoot. The
metal-removal potential of endophyte-inoculated plants was significantly higher than
control as the endophyte-association mediated the Cu uptake via roots into shoots.
The symbiosis rescued the host-plant growth by minimizing Cu-induced electrolytic
leakage and lipid peroxidation while increasing reduces glutathione activities to
avoid oxidative stress. P. funiculosum-association synthesized higher quantities of proline and glutamate as compared to
control. Stress-responsive abscisic acid was significantly down-regulated in the plant-metal-microbe
association.

Conclusion

The endophyte P. funiculosum symbiosis counteracted the Cu stress and reprogrammed soybean plant growth. Such
growth promoting and stress mediating endophytes can be applied at field levels to
help in bioremediation of the polluted agricultural fields.